Dry spinning process for making y-shaped filaments



P L- D. w. RAYNOLDS ET AL 7 2,829,027

DRY SPINNING PROCESS FOR MAKING Y-SHAPED FILAMENTS Filed Dec. 28, 1955 I 2 Sheets-Sheet 1 Fig.1

David WRayno/ds FrankWAbernaMy Ari/tar (Sf Smiflz INVENTORS April 1, 1958 D. w. RAYNOLDS ET AL 2,829,027

DRY SPINNING PROCESS FoR MAKING YSHAPED FILAMENTS Filed Dec. 28, 1955 2 SheetsSheet 2 SECTION OF SP/NNERETTE SHOW/N6 F1 9- 2 ONE OR/F/CE ig- PRIOR ART David WRagno/ds E'r'ank WAbernaf/zy Arlhur 8. nzifiz INVENTORS BY @Mwz J ATTORNEYS United States Patent DRY SPINNING PROCESS FOR MAKING Y-SHAPED FILAMENTS David W. Raynolds, Frank W. Abernathy, and Arthur S. Smith, Kingsport, Tenn., assignors to Eastman Kodak fompany, Rochester, N. Y., a corporation of New ersey Application December 28, 1953, Serial No. 400,564

6 Claims. (Cl. 18-54) This invention relates to the preparation of synthetic filaments and fibers of increased bulk and stiffness as Well as increased luster and covering power. larly this invention relates to improved dry spinning methods and apparatus for producing from cellulose ester spinning solutions filaments and fibers of a Y-shaped cross-section having such improved characteristics. Furthermore this invention also relates to fabrics and other articles of manufacture made of, or containing such novel Y-shaped cross-section filaments and fibers.

Heretofore, various processes and apparatus have been provided for the production of synthetic filaments and fibers of various cross-sections. Generally these wellknown cross-sections fall within one or two classifications such as relatively narrow and rectangular crosssections, or rounded cross-sections which include filaments of round and fiat sides, clover-leaf configurations and other related variations produced by physically deforming the filament, after it has assumed its normal shape, as it issues from-the spinning cabinet.

Typical methods and apparatus for dry spinning solutions into synthetic fibers are disclosed in U. S. Patents.

2,000,047 and 2,000,048 of May 7, 1935, to H. G. Stone. These patents describe methods including the forcing of a heated cellulose ester spinning solution through a spinnerette having a plurality of separated circular orifices and into a drying chamber containing an evaporative atmosphere maintained at a suitable-drying temperature. By such controlled conditions filaments can be consistcntly formed of approximately round or clover-leaf crosssection as contrasted to'the filaments previously produced of elliptical shape.

Also, as shown in U. S. Patent 1,695,455 of December 18, 1928, by drawing the filaments from a round or circular orifice spinnerette in a direction other than perpendicular to the horizontal face of the spinnerette, filaments having a more or less flattened cross-section are produced. It is also known that slight variations from the round cross-section can be caused by adjusting the particular evaporating conditions under which the filaments are dried in the spinning cabinet. A suitable selection of these conditions will permit the production, from spinnerettes having round orifices, of filaments with either a smooth or an unsymmetrical irregular surface.

In U. S. Patent 1,773,969 of August 26, 1930, the technique of the extrusion of filament forming solutions through circular orifices into evaporative atmospheres is also discussed. As described therein, it is suggested that the outer layer of the stream of cellulosic material which is initially circular in cross-section as it issues through the spinnerette orifices hardens or solidifies, first More particu iii forming a skin that is tougher and less fluid than the interior. After this initial hardening of the outer surface, the interior of the filament is dried and thereby solidified and shrinks while the outer layer is further hardened. The outer shell of the filament being tougher and more determined in shape than the interior, the

contraction of the volume of the interior causes the outer film or layer to collapse and to assume a very irregular cross-section which is in the form of a figure of many indentations of varying sizes and shapes and which is often quite flat. Because of the irregularity of shape and flatness of the cross section of such filaments, their covering power, their bulk, stiffness and luster are quite irregular. This Patent 1,773,969 then describes the use of spinnerette's having orifices of compact or squat shape having indentations in the form of re-entrant angles. The re-entrant angles can be constituted by straight or curved boundary lines. However, the filaments produced by extruding celluloseesterfil'amem forming solutions through such orifices have cross-sections more or less characterized by rounded surfaces.

As described in Hickey Patent 2,373,892 of April 17, 1945, I-beam type cross-section filaments or fibers having a high degree of resiliency and crush resistance may be produced by extruding a suitable cellulose ester solution through a spinnerette having rectangular orifices, the ratio of the length to the width of each rectangular orifice being between 1.35 and 1.65. Fibers made from such l-beam filaments are particularly useful for manufacturing carpet materials, as well as for the manufacture of rugging and other pile fabrics. However, the ends of the I-beam are of a round shape and do not extend substantially above the fiat section of the I-beam.

An object, therefore, of the present invention is to provide a process for preparing filaments and fibers with an increased bulk and stiffness as compared to the above discussed prior art fibers of equivalent denier and chemical composition.

Another object of this invention is to provide'a process for preparing filaments and fibers of increased surface area as compared to the above discussed fibers known heretofore in the art to which this invention relates.

Still another object of this invention is to provide synthetic filaments and fibers of Y-shaped cross-section of the nature hereinafter described.

A further object of this invention is the preparation of the desired filaments and fibers from spinnerette orifices of a simplified design that can be easily and accurately manufactured. V 1

Yet another object of this invention is to provide a spinnerette having extrusion orifices therein of equilateral triangular shapes.

Another object is to provide staple fibers made from a plurality of filaments having Y-shaped cross-sections.

Again another object is to provide new and novel fabrics having a crisp feel, improved covering power and luster containing such Y-shaped cross-section filaments or staple fibers.

Still another is to provide a novel filling material of increased resistance to matting which is suitable to employ in pillows and the like.

Yet another object of this invention is to provide fibers adaptable for use in manufacturing cigarette filters.

Other objects will appear hereinafter.

In accordance with the present'invention these and other objects may be attained by forcing a suitable spinning solution through a spinnerette having a plurality of equilateral triangular shaped filament forming orifices therein and evaporating the solvent by drying the resulting filaments in a spinning cabinet under carefully controlled conditions of temperature while subjecting the filaments to predetermined drafting. The temperature -face area.

orifices temporarily assume a triangular cross-sectional shape. However, in accordance with a surprising feature of our invention, by careful control of the extrusion rate,

the drafting rate and drying temperatures, we have dis covered there occurs a change in the filament cross-section is uniform along the length of the filament.

Under optional conditions of operation it is possible to vary the length, shape and angular position of the legs of theY. However, such modifications of crosssectional filament structure are not preferred since they result in the production of filaments of less bulkiness and luster, and such filaments tendto mat together to an undesirable extent under certain conditions.

In general the spinnerette having the equilateral triangular orifices may be employed with any suitable spinning cabinet such as, for example, one of the form illustrated in U. S. Patents 2,000,047 and 2,000,048 referred to above. The Y-shaped cross-section filaments, however, can be prepared in accordance with our invention within a satisfactory range of spinning, drafting and solution conditions as is described hereinafter.

Another unusual and interesting feature of our invention is the discovery that filaments produced in accordance therewith by extruding solutions of cellulose acetate through equilateral triangular orifices have a more perfect Y-shaped cross-section than is obtainable when a spinnerette having Y-shaped cross-section orifices is employed. In fact, in the latter case the filaments generally fall within the above-named prior art classifications and are of a distorted rounded configuration and of non-uniform cross-section. They exhibit none of the desirable properties possessed by our novel filaments.

As previously stated above, we have found that the Y- shaped cross-section filaments and fibers of our invention have much greater bulk and stiffness than similar filaments or fibers of rounded cross-sections heretofore known in this art. These characteristics of our filaments and fibers appear to be due to the intermeshing of the legs of the Y of the individual filaments in the filaments bundlein such manner that each is reinforced by the other and the filament ,bundle has a resultant stiffness greater than that possessed by the normal cross-section fiber of equivalent denier because of the increased sur- It is noted that acircle taking in the three tips of the legs of the Y will be greater in diameter than one taking in the lobes of the well-known clover-leaf type of cross-section. This larger circle" is, therefore, the

effective area of the Y-shaped cross-section and explains the increased bulkiness of our novel Y-type of filament and fiber.

The present invention will be further understood by reference to the following detailed description in which several examples of our invention are given and to the related drawings in which: a

Figure 1 is a schematic elevational view, partly in section, showing a spinnerette which has equilateral triangular filament forming orifices positioned in a suitable dry spinning cabinet which is equipped with suitable auxiliary apparatus;

Figure 2 is a view of the face of a spinnerette showing a plurality of filament forming orifices of equilateral triangular shape; I

Figure 3 is a greatly enlarged representationof the spinning solution coming out of theft'riangular orifices of the spinnerette and forming into the, Yrsl iaped cross-section filaments;

Figure 4 is a reproduction of an actual photomicro- 4 graph showing the cross-section of several Y-shaped filaments of the present invention; and

Figure 5 is a reproduction of an actual photomicrograph showing in cross-section several clover-leaf filaments made by a prior art method.

The similar parts in the several figures are identified by the same numerals.

Referring to Figure 1 there is shown schematically a side elevation view, partly in section, of a spinning cabinet ll and its associated apparatus by which the novel Y-shaped synthetic filaments and fibers of the instant invention may be manufactured. Mounted at the top of the cabinet is a candle filter unit 12 to which is connected a spinnerette 13 which in accordance with our invention has a plurality of orifices 14 therein which are of the shape of equilateral triangles. The face of this novel type of spinnerette with the equilateral triangular orifices 14 therein is shown in the greatly enlarged view of Figure 2. The candle filter may be uniformly heated by means of heating coils, not shown, which are positioned so as to surround candle filtcr 12, and through which coils may be circulated any appropriate heat exchange medium such as water maintained at the desired tcmperaturc.

Spinning solution of composition described hereinafter is supplied from conduit 16 through valve 17 to pump 18 which forces the solution at the desired rate to the candle filter unit 12, thence to spinnerette 13 through the equilateral triangular orifices 14 from which it is extruded initially in the form of equilateral triangular filaments 25.

The filaments 25 pass downwardly in the cabinet 11 while progressively losing solvent by evaporation until, in a substantially solidified condition they leave the cabinet 11 and pass around godet roll 20, which is positioned below the lower end of the spinning cabinet ll. Godet roll 20 is driven at a uniform speed by means, not shown, to give the desired draft to the filaments 25. From godet roll 20 the filaments pass over the usual guide rolls, one of which is shown at 21, and are finally wound onto a bobbin 22 after an appropriate twist has been imparted I thereto, if desired, by means not shown.

,nection with Figure 1.

To facilitate the evaporation of solvent from the filaments during their travel through the cabinet, heated air is supplied to the cabinet 11 by means of inlet conduits 23 and 24 positioned respectively adjacent the lower and upper ends thereof, the air passing through the cabinet and emerging through outlet conduit 26 positioned at a substantial distance below spinnerette 13, as illustrated.

The change of the cross-section of the filaments while in the cabinet from an initial triangular cross-section shape to the desired Y cross-section shape is illustrated in Figure 4. As shown at 25 the filaments have just EXAMPLE 1 V A spinning solution consisting of 26.5% cellulose acetate, 1.25% titanium dioxide, based on the weight of the cellulose acetate, 1.75% water and the remainder being the solvent, acetone, was spun into Y-shaped cross-section filaments of 55 denier per strand using the apparatus and'its general operation as described above in con- The spinnerette had 13 equilateral triangular orifices therein. The conditions of operation are shown in Table I where they are identified as No. 1.

In this table the air flow in cubic feet per minute is calculated per one hundred spinning cabinets. The

7 figures-under the spinnerette orifice column represent-one side of the equilateral triangle. The extrusion speed in meters per minute represents the rate at which the spinning solution is forced out of the spinnerette. This, in cooperation with the draft rate enables the filaments EXAMPLE 5 Another spinning solution consisting of 26.5% cellulose acetate, 0.6% titanium dioxide pigment, based on the weight of the cellulose acetate, 1.75% water andthe to change from the initial triangular cross-section to 5 remainder e g acetone solvent was p o p d the Y cross-section whileproperly curing. cross-section filaments of 55 denier per strand. The same Table I N o. Fila- Extru- Candle Extru- Top Air Bottom Spinner- Denier ments sion Filter sion Top Air Bottom Inlet Air Inlet ette No. Per For Speed, Temp, 'lemp., Flow, Air Flow, Temp, Temp., Orifice, Draft Strand Strand Meters 0. 0. C. F. M. O. M. 0. 0. ill inute meters 55 13 500 500 500 70 85 0. 067 i. 75 19 500 500 500 70 85 0.067 1. 10 150 as 500 800 800 70 85 0. 067 1. 10 150 7 211 500 500 60 90 0. 155 1. 22 as as 500 500 500 60 85 0. 047 1. 43 75 49 500 500 500 60 85 0. 047 1. 43 300 7 100 1, 500 1, 500 60 90 0. 220 1.08

Draft ratio may be defined rather broadly as the ratio spinning equipment was employed with the operating of the linear velocity of wind-up of the filaments to the conditions shown as No. 5 in Table I. linear velocity of extrusion of the spinning solution. More specifically, draft ratio maybe defined as the ratio 25 EXAMPLE 6 of the linear velocity at which the filaments are wound onto and off the godet roll of a dry spinning cabinet to the calculated average linear velocity at which the quantity of spinning solution necessary to the formation of any one of the plurality of filaments comprising the bundle of filaments Wound onto and off the godet roll is extruded through any one of the plurality of orifices in the spinnerette employed in the spinning operation, the velocities being expressed in the same units of distance per unit time. up at the godet roll at the same linear velocity that the spinning solution is extruded from the spinnerette, the draft is 1.0, thus signifying that the linear speed of windup is 100% of the extrusion speed. Similarly, if the filaments are Wound up or withdrawn from the cabinet at For example, if the filaments are wound the godet roll at a linear speed 50% greater than the speed of extrusion, the draft is 1.5, and so on.

Other columns of Table I are more or less self explanatory when considered in connection with Figure 1 of the drawings and the related description. Temperatures in the drying cabinets averaging from to 90 C. are usable.

EXAMPLE 2 EXAMPLE 3 The cellulose acetate spinning'solutionof Example 1 was spun into Y-shaped cross-section filaments of 150 denier per strand. The spinnerette had 38 equilateral triangular orifices. The above described spinning equipment was used with the operating conditions shown as No. 3 in Table I.

EXAMPLE 4 A different spinning solution consisting of 30.0% cellulose acetate, 1.75 water and the remainder being acetone solvent Was spun into Y-shaped cross-section filaments of 150 denier per strand. The spinnerette had 7'equilateral triangular orifices. The above described spinning equipment was used with the operating conditions shown as No. 4 in Table I.

EXAMPLE 7 A spinning solution consisting of 26.5% cellulose acetate, 1.75% water, the remainder being acetone was spun into Y-shaped cross-section filaments of 300 denier per strand. The spinning equipment herein described was employed using a spinnerette having 7 equilateral triangular orifices. Conditions of operation are shown as No. 7 in Table I.

We have found that excellent Y-shaped cross-section filaments can be prepared under a relatively wide range of spinning and solution conditions. A primary requisite for optimum Y-shaped cross-section yarn is that the spinning draft should be above 1.0 and preferably above 1.2. However, somewhat deformed Y-shaped cross-section filaments may be obtained using spinning drafts of 0.7 to 1.0. But as indicated above, for purposes of attaining uniformity of cross-section a draft above 1.0 is preferable.

The temperatures listed in Table I are temperatures used to produce a quality product with a particular cellulose ester-acetone solution. These temperatures are not too critical and may vary over a substantial range. Changes in cellulose esters and cellulose ester to acetone ratios may require some alterations or changes in these temperatures.

While particular emphasis has been made to preparing Y-shaped cross-section filaments from cellulose acetate, our process will also operate satisfactorily with the single and mixed organic acid esters such as those containing 2 to 4 carbon atoms.

We have also found that our spinning process employing spinnerettes having equilateral triangular orifices operates very well over a range of deniers .per filament of 1.5 to 43, although higher denier filaments can be satisfactorilymade by. our invention.

That the bulk of the Y-shaped cross-section fiber, because ofits particular cross-sectional shape and increased surface area, is greater than the clover-leaf or regular cross-section fiber of equivalent denier is shown clearly in the following Table II where comparisons of equivalent samples of regular and Y-shaped cross-section yarn made from the same spinning compositions are set forth.

I 7 Table 11 BULK TESTS ON REGULAR AND Y CROSS-SECTION CONTINUOUS FILALIENT YARNS In Table II the numerical expressions 55/ 13/3 and the like represent continuous filament yarn in terms of total denier, filament count, andtwist. For example, 55/ 13/3 designates a continuous filament yarn having a total denier of 55 made up of 13 filaments and having 0.3 turn per inch of twist. The denier per filament of such a yarn is the total denier divided by the number of filaments. In this example 55 divided by 13 equals approximately 4 denier per filament.

The data in Table II are determined by a test which we have developed in which yarn is wound under a specified tension until it fills a spool of a known volume. amount of yarn required to fill this volume is weighed. From this weight the bulk factor and specific volume are calculated. The bulk factor is calculated by the following formula:

(Volume of spool density of fibers+weightof yarn to fill spool) 100=bulk factor This formula expresses the bulk as a percentage ratio of the space occupied by the yarn to the space which would be occupied by solid material from which the yarn is made.

The specific volume is determined by converting the weight of yarn on the spool to cubic inches per pound- The column shown as percent difference expresses as a percentage, the percentage difference between the bulk factor, or the specific volume, in the regular and Y section yarn; It will be noted that in continuous filament yarn the Y-shaped yarn has from 29.6 to 41.0% more bulk than regular yarn. This difference can be seen visually when comparing the skcins from which these data were obtained.

Similar data are shown in Table III relative to staple fiber yarn made respectively from regular and Y section fibers of the same cellulose ester composition.

Table III BULKTESTS ON REGULAR AND Y CROSS-SECTION STAPLE FIBERS Bulk Specific Percent Yarn Factor Volume Difference Cu.In./Lb.

Regular 20/1, 2 D/F, 2 282. t). 2 Y 1, 2 D/F, 2" ass. 0 81.9 i Regular 20/1, 3 D/F, 2" 202. 0 55.2 V 20/], 3 D/F, 2 405.0 85. 0 Regulnr12/1, 5 D/F, 2" 267. 5 56. 3 1 Y 12/1, 5 D/F, 2 368. 0 77. 4 v

The

"8 tion, denier and length and varying only in cross-section, i. e. between regular and Y section, that the Y section staple has from 37.4 to 54.2% more bulk.

The luster of the Y-shaped cross-section yarn is appreciably greater than that of the regular or clover-leaf cross-section of equivalent denier and composition. Luster is measured by means of a photo-electric cell. The filaments are wound in a. parallel manner around a flat piece of cardboard or other similar flat surface. Light refiected off these panels to the photoelectric cell imparts a potential which is translated into a numerical luster level. On comparative tests the clover-leaf panel of filaments record 0.77 volt whereas the Y cross-section filaments of the same denier record 0.83 volt.

EXAMPLE 8 Staple fibers made from Y-shaped cross-section cellulose acetate yarn were employed as a filling material in a pillow. Because of their bulk they were found to be satisfactory for this purpose. A similar sized pillow containing the same weight of cellulose acetate staple fibers of equivalent denier of regular cross-section evidenced less bulk and did not resist matting under pressure.

EXAMPLE 9 Cigarette filters were prepared from Y-shaped crosssection cellulose acetate fibers. Their interesting bulk and stiffness properties permit the construction of filters of interesting design.

We have noted that yarns composed of Y-section filaments are much stiffer and more resilient than yarns having normal or clover-leaf cross-sections. The effect on stiffness of cross sectional shape can beestimated by comparing moments of inertia of fibers having different shapes but the same cross sectional area. By this method we have determined that Y-section filaments are approximately 60% stiffer than normal filaments of equal size. Furthermore, we have found that when a plurality of Y-shaped filaments are collected in a bundle as in a yarn strand or in a batting, a greatly increased resilience or stiffness is noted which ismore than would be expected from the increase in stiffness of individual fibers. We attribute this effect to .the interlocking or tongue and groove mingling of the legs of the Y-filaments making up the mass of fibers. This interlocking of fibers causes much greater resistance to interfiber slippage than can be obtained in a bundle of normal filament. Thus the aggregate stiffness of a bundle of Y filaments is much greater than the sum of the stilfnesses of the individual fibers.

The inherent properties of cellulose acetate fibers of the Y-shaped cross-section are such that they offer numerous desirable properties in both woven and knitted fabrics. In such fabrics as ninons, marquisettes, and voiles, the Y-shaped section fibers produce fabrics having desirable crispness and stiffness which are usually obtained only by special processing techniques or by special finishing In fiat fabrics, such as taffetas, twills, and satins, the increased bulk of the Y-shaped fibers produce fabrics having greater cover and thickness for a given weight of material. 0n the other hand there is the possibility of using less material to produce fabrics of the same cover and thickness thereby decreasing the cost. Yarns having a Y cross-section produce fabrics with less tendency for the yarns to slip resulting in higher seam strength. This characteristic is particularly important in certain fabrics, for example, satins and twills. Loom finished taffetas have a crisper feel when made from Y section yarns.

Knitted fabrics from yarns with Yshaped sections exhibit increased body and hand which make them more desirable for certain uses such as sport shirts, mens ties, and dress goods. Yarns spun from staple fibers of-Y cross-section exhibit increase in bulk and stiffness as do the filament yarns. In addition, fabrics from these yarns have a wool-like feel or hand. In all of the fabrics which have been produced from cellulose acetate fibers of the 9 Y-shaped cross-section fabric properties have been obtained which are desirable and which are not obtained in cellulose acetate fibers of regular cross-section.

We claim:

1. The method of forming cellulose organic acid ester filaments having a Y-shaped cross-section, the legs of the Y being substantially equal in length and the angles between adjacent legs of the Y being substantially equal, which comprises extruding a cellulose organic acid ester filament forming solution through a spinnerette equipped with equilateral triangular extrusion orifices and into a dry spinning cabinet, drafting the filaments at a draft ratio within the range of approximately 0.7 to 1.4 while drying the filaments.

2. The method of forming cellulose organic acid ester filaments with a Y-shaped cross-section, the legs of the Y being substantially equal in length and the angles between adjacent legs of the Y being substantially equal, which comprises extruding a cellulose organic acid ester filament forming solution through a spinnerette equipped with equilateral triangular extrusion orifices and into a dry spinning cabinet, drafting the thus formed triangular cross-section filaments at a draft ratio within the range of approximately 1.10 to 1.43 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby the cross-section of the filaments is changed to said Y cross-section.

3. The method of forming cellulose acetate filaments with a Y-shaped cross-section, the legs of the Y being substantially equal in length and the angles between adjacent legs of the Y being substantially equal, which comprises extruding a cellulose acetate filament forming solution through a spinnerette equipped with equilateral triangular extrusion orifices and into a dry spinning cabinet, drafting the thus formed triangular cross-section filaments at a draft ratio within the range of approximately 1.10 to 1.43 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby the cross-section of the filaments is changed to said Y cross-section.

4. The method of forming cellulose acetate filaments with a Y-shaped cross-section, the legs of the Y being substantially equal in length and the angles between adjacent legs of the Y being substantially equal, which comprises extruding a cellulose acetate filament forming solution through a spinnerette equipped with equilateral triangular 10 extrusion orifices and into a dry spinning cabinet, drafting the thus formed triangular cross-section filaments at a draft ratio of approximately 1.2 while drying the filaments at an average temperature within the range of C. to C. whereby the cross-section of the filaments is changed to said Y cross-section.

5. The method of forming cellulose acetate filaments with a Y-shaped cross-section, the legs of the Y being substantially equal in length and the angles between adjacent legs of the Y being substantially equal, which comprises extruding a cellulose organic acid ester filament forming solution through a spinnerette equipped with equilateral triangular orifices of the same size and into a dry spinning cabinet, drafting the thus formed triangular cross-section filaments at a draft ratio of approximately 1.1 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby the cross-section of the filaments is changed to said 'Y cross-section.

6. The method of forming cellulose acetate filaments with a Y-shaped cross-section, the legs of the Y being substantially equal in length and the angles between adjacent legs of the Y being substantially equal, which comprises extruding a cellulose acetate filament forming solution through a spinnerette equipped with equilateral triangular orifices of the same size and into a dry spinning cabinet, drafting the thus formed triangular cross section filaments at a draft ratio of approximately 1.4 while drying the filaments at an average temperature within the range of 60 C. to 90 C. whereby the cross-section of the filaments is changed to said Y cross-section.

References Cited in the file of this patent UNITED STATES PATENTS 2,000,047 Stone May 7, 1935 2,000,048 Stone May 7, 1935 2,013,688 Kinsella Sept. 10, 1935 2,026,730 Dreyfus Jan. 7, 1936 2,313,296 Lamesch Mar. 9, 1943 2,373,892 Hickey Apr. 17, 1945 2,387,791 Hofiman Oct. 30, 1945 2,434,533 Wurtzburger Jan. 13, 1948 2,588,583 Small et al. Mar. 11, 1952 2,588,584 Small Mar. 11, 1952 2,673,368 Denyes Mar. 30, 1954 2,677,184 Webb May 4, 1954 

1. THE METHOD OF FORMING CELLULOSE ORGANIC ACID ESTER FILAMENTS HAVING A Y-SHAPED CROSS-SECTION, THE LEGS OF THE Y BEING SUBSTANTIALLY EQUAL IN LENGTH AND THE ANGLES BETWEEN ADJACENT LEGS OF THE Y BEING SUBSTANTIALLY EQUAL, WHICH COMPRISES EXTRUDING A CELLULOSE ORGANIC ACID ESTER FILAMENT FORMING SOLUTION THROUGH A SPINNERETTE EQUIPPED WITH EQUILATERAL TRIANGULAR EXTRUSION ORIFICES AND INTO A DRY SPINNING CABINET, DRAFTING THE FILAMENTS AT A DRAFT RATIO WITHIN THE RANGE OF APPROXIMATELY 0.7 TO 1.4 WHILE DRYING THE FILAMENTS. 